There comes a time in most fish keepers' lives when the problem of dreaded algae rears its head.

Not all algae in the aquarium is bad, indeed some fish positively need it and it’s virtually impossible to be completely algae free when you are combining water with light and nutrients. It tends to be related to a number of issues which, with a little care and some changes to the tank set up and maintenance regime should reduce the problem. Sometimes it may be too much light, or not enough. Sometimes too many nutrients that the plants cant use before the algae does. High levels of phosphates and silicates in some regions may also exacerbate the problem.

Common types of Algae

Brown diatom algae - common in new tank set ups but it can appear in established tanks if the conditions are right. It should disappear as the tank settles but can last for a few weeks or so. It mainly affects the gravel and plants and looks like a pale brown sludgy coating that can be wiped off with the fingers.

Green Spot Algae - appears as little green spots mainly on the glass. A very common type of algae which magnet algae cleaners struggle to contend with. It can be treated simply by way of a specific aquarium cleaner like the Hobby Glass Cleaner which has a razor blade between the magnets.

Hair Algae – is usually seen on plants and sometimes the decor. It ranges in colour from grey to green and some strands can grow very long quite quickly, up to several inches. Winding a toothbrush around it removes the most heavily affected leaves. Very common on plants and rocks. Can be many different colours but is usually green or greyish. They are long thin strands sometimes growing 3-4 inches long. Normally due to overdosing of liquid fertilisers, especially ones high in iron and phosphates.

Staghorn Algae – as the name suggests this is longer quite filamentous algae with parts ‘branching off’ resembling stags' horns! Usually grey in colour it tends to grow along the outside edges of leaves.

Red Brush Algae – is usually seen as fine threads clumped together in little hairy tufts.

Black Brush Algae – as above but as the name suggests black or dark grey.

Blue Green Algae (BGA also known as Cyanobacteria) – technically, this is not actually an algae but a form of bacteria. Poor circulation in tanks may be a contributing factor. Usually it appears as a thin dark blue green slimy coating that will cover plants décor and substrate. No fish is known to eat this as it is quite toxic. Stripping the affecting areas out of the tank and diligent daily maintenance may be required.

Changes you can make that will help…..

Don’t despair, there is a multi-pronged attack to get rid of/reduce algae problems:

1. How long are your tank lights on for? If you are not already doing it, try a light siesta. Most fish keepers apart from those lucky enough to have no algae problems at all do so. 4 hours on, a few hours break, then another 4 hour period. A domestic timer like the ones B&Q sell fair well. You may be able to up it to 5 hour tranches if you are lucky. You can use blue LED moonlights for times in between or for night time viewing (these replicate the moon) and these don't increase any algae growth. Tanks should never be placed near windows or have direct sunlight on them. If the position of the tank is affected by this, it should be moved.

2. What is your tap water reading for phosphates? You can purchase phosphate testing kits from a good LFS or the internet. Ideally, phosphate levels should be low to nil but some areas have readings in excess of 5ppm. If your readings are high there are phosphate removers you can buy. Commonly used brands are Rowaphos, Phosban and Seachem Phosphate remover. You add this to a little bag (or the end of a stocking) in the filter. Very effective but it does get exhausted quite quickly depending on the levels in your water. Sometimes replacing each month will be needed but the water tests each week will show you when phosphate starts to rise again, if you invest in the tester kit.

3. What are dosing, fert wise? If you are adding plant fertiliser on a weekly basis with the water change, consider switching instead to smaller doses on a daily basis. Dosing a large amount of fertiliser without the plants' ability to use it all up fairly quickly just leaves excess in the tank for the algae to enjoy. Are you dosing an excess of some nutrients and not enough of others? This is a little ‘trial it and see’ though.

4. How many real plants are in the tank? If you only have plastic or silk plants, you need live ones. If you have live ones, you probably need more live ones! The more live plants the better to out compete the algae. Give the old ones a good hair cut if required and remember that plants compete with the algae, hopefully using up the nutrients before the algae gets a chance. It doesn’t need be expensive – lots of nice cheap fast growing stem plants seem to work well (Elodea, Hornwort etc). Throw in a number of moss balls too as these seem to work wonders.

5. What is the water circulation like in the tank? Dead spots and areas of poor water circulation are more likely to be affected by some kinds of algae (especially the BGA kind). Air stones and bubble curtains effectively deal with dead spots, adding an additional power head perhaps on bigger tanks also helps. You should be aiming for some increased gentle circulation though as opposed to an excessive cauldron of bubbles. Too much disturbance will drive off the co2 in the tank which you also need, to assist with plant growth – see below.

6. Should more co2 be added? Planted tanks do benefit from the addition of co2 but it’s not a route that some people really want to take when they start off fish keeping. Yes, it can be a little daunting with the extra equipment that is needed and steps 1 to 5 above may resolve the problem. The addition of co2 warrants an entire article of its own and this is not the aim of this particular guidance. It should not be discounted though, where the aquarium keeper feels confident enough to explore this addition.

Late Note: The plant Ceratophyllum Demersum, commonly known as 'Hornwort', produces an excretion that discourages algal growth. Worth adding to any tank either planted or just floating in the water as it may assist too.